Basics about constructed wetlands

Plant treatment plants are a possibility of biological wastewater treatment, which offers some advantages over other small sewage treatment plants, but also has some disadvantages. You will therefore find out everything important about constructed sewage treatment plants here and in the following articles.

Functioning of the sewage treatment plant

After a mechanical pre-cleaning, in which all solids contained in the wastewater are first separated, the so-called yellow water is introduced into the plant treatment plant.

In the actual cleaning tank, a clarification of the wastewater takes place mainly by the contained plants and microorganisms, after the small wastewater treatment plant can be connected in addition to a fining pond in some cases. But that is not absolutely necessary and is merely a voluntary additional measure.

The disposal of purified by the plant water treatment plant is either in a receiving water, or more rarely by trickling or discharge into groundwater, if no suitable receiving water is available.

From their design, plant water treatment plants can be designed very differently. The most common type are overgrown horizontal or vertical filter plants, as listed in the DWA 262. In addition, there are also many other possibilities of execution.

Different plant sewage treatment plant types

  • Hangverrieselung
  • overflowed wetlands
  • floating Islands
  • Plants with sewage sludge

Even with the overgrown soil bodies, the type of plant to which also horizontal and vertical filter plants belong, there are various possibilities of execution. Occasionally there are also retention soil filter systems or specially designed root canal sewage treatment plants.

Expiring cleaning procedures in constructed wetlands

Depending on the type of PCA, different cleaning processes take place. The biological and biochemical events in a PCA are extremely complex and largely correspond to the processes that take place in nature.

An important role is played by planting, usually reeds or related crops, which fulfill several functions: they absorb most of the wastewater components they use for their growth. Their roots loosen up the soil, increasing the oxygen permeability of the soil.

Further purification of the water is carried out by the microorganisms that live firmly attached to the soil. They purify the water by triggering various biochemical processes. This is called the principle of biological wastewater treatment.

Particularly effective are plant sewage treatment plants with regard to the removal of nitrogen from the wastewater. Phosphorus and ammonia contained in many effluents can also be virtually completely removed from the plant water treatment plant.

Economic efficiency of constructed wetlands

Depending on the plant type and structure, the cost of constructing a wetland plant is low. The effort for operation and maintenance is also limited. In the case of sewage treatment plants, compared to sewage ponds, a constant high cleaning performance is given which is independent of the weather conditions.

Ecological compatibility

They can last for decades without major repairs. Here, the clarification of the water takes place purely biological way. Some types of systems can be done without external energy. This makes them a very ecological alternative.

Open water systems can also bind large amounts of CO2 and thus fulfill a further added benefit. A plant treatment plant can be harmoniously integrated into the landscape. As a disadvantage, however, one can see the comparatively large space requirement for other types of small sewage treatment plants.

Dimensioning of constructed wetlands

Plant treatment plants are always dimensioned according to the so-called population value. The population equivalent or population equivalent is the amount of wastewater generated by an average inhabitant.

The smallest possible sizing in wetlands are 4 population equivalents. The area required is approximately 4 - 5 m² per inhabitant. The smallest possible system size for a single-family home thus requires an area of ​​around 20 square meters.

Tips & Tricks

Different types of plants have different levels of clarification in certain areas. Therefore, it makes sense to adapt the system type as exactly as possible to the required method of clarification. This ensures a high drainage quality.

Video Board: Constructed Wetlands for Wastewater Treatment